1. Field of the Invention
The present invention relates to an optical displacement detecting device, such as an encoder, a velocity sensor or an acceleration sensor for measuring displacement or velocity of an object, utilizing a fact that a light beam diffracted, or scattered by an object being displaced is subjected to phase modulation corresponding to the displacement or the velocity of the object.
2. Related Background Art
Conventionally, optical displacement sensors for precisely determining the physical amounts such as displacement of an object by irradiating the object with light, for example, an optical encoder, a laser Doppler velocimeter or a laser inteferometer, are widely utilized principally in the fields of NC working machines, OA equipment, robots or the like. As conventional examples of such displacement sensors, an optical encoder is disclosed for example in the Japanese Utility Model Laid-open Application No. 1-180615 and in the Japanese Patent Laid-open Application No. 62-121314. Also, a laser Doppler velocimeter is disclosed in the Japanese Patent Laid-open Application No. 2-262064.
For wider applications of such displacement sensors, there are desired further compactization (to the order of millimeters) and a higher precision and a higher resolution (in the order of 0.1 .mu.m). A size in the order of millimeters will enable the field of application to be wide, since such a device can be used on smaller objects for example by direct adhesion thereon.